Rotary jar

ABSTRACT

A rotary jar is disclosed for use in well bores when a tool, attached to the jar, becomes so stuck that normal tension on the drill string will not release it. The rotary jar has an outer housing and an inner mandrel with appropriate seals therebetween defining an annular working chamber. A knocker is attached to the mandrel and an anvil is attached to the housing. The working fluid in the working chamber exhibits low viscosity changes with high temperature changes. Within the chamber are located a piston and a valve combination so arranged that when the drill string is under high tension, fluid is forced in minute quantities through the valve combination. This is actually a mutual extension of the mandrel and housing which continues until the piston and valve combination come into contact with an annular sleeve in the chamber. The sleeve moves with the piston and valve combination allowing fluid to dump therebehind, thereby allowing the knocker and anvil to come into jarring contact. Provision is made for resetting the jar so that it may be operated continuously over over long periods of time.

United States Patent 1 Griffith [4 1 Feb. 13, 1973 ROTARY JAR WilliamEarl Griffith, Okotoks, Al-

[75] lnventor:

. berta, Canada Primary ExaminerDavid H. Brown Attorney-Weir, Marshall,MacRae & Lamb ABSTRACT A rotary jar is disclosed for use in well boreswhen a tool, attached to the jar, becomes so stuck that normal tensionon the drill string will not release it. The rotary jar has an outerhousing and an inner mandrel with appropriate seals therebetweendefining an annular working chamber. A knocker is attached to themandrel and an anvil is attached to the housing. The working fluid inthe working chamber exhibits low viscosity changes with high temperaturechanges. Within the chamber are located a piston and a valve combinationsov arranged that when the drill string is under high tension, fluid isforced in minute quantities through the valve combination. This isactually a mutual extension of the mandrel and housing which continuesuntil the piston and valve combination come into contact with an annularsleeve in the chamber. The sleeve moves with the piston and valvecombination allowing fluid to dump therebehind, thereby allowing theknocker and anvil to come into jarring contact. Provision is made forresetting the jar so that it may be operated continuously over over longperiods of time.

10 Claims, 3 Drawing Figures mummi- ROTARYJAR The present inventionrelates in general to drilling equipment and more particularly to rotaryjars for releasingtools trapped in well bores.

Well jars are extensively known in the prior art and they are of twogeneral types, mechanical and hydraulic. Each type has its ownparticular disadvantages, the mechanical suffering from accelerated wearand the hydraulic sufferingfrom viscosity changeswith temperature.During a jarring operation, the jar may be activated as often as two orthree times a minute, for

' periods of up to many days, and the internal parts of the jarcould besubject to very high pressures, at times as much as 50,000 or 60,000P.S.I. When a well-tool is so stuck in the bore that tension alone willnot release it, it becomes extremely vital that a jar, if used, be inperfect working order. A jar that has failed is of no use, and itbecomes probable that the stuck tool will be lost if the drill stringbreaks under tension.

The rotary jar .of the present invention overcomes the problems of theprior art devices by providing a rotary jar having an inner mandrel, anouter housing, a knocker and anvil in conventional relationship, pistonand valve means wherein the valve contains no moving parts and istemperature variable and a working fluid of Silicone 200 which exhibitsvery small viscosity changes over a wide temperature range. The valvemeans permits minute quantities of the working fluid to pass from aworking chamber above the piston to a chamber below the piston, duringoperation of the rotary jar. When the piston and valve means areadjacent a movable sleeve in a recess within the housing, the sleevewill lift from its seat in the recess to permit the fluid remaining inthe working chamber to dump behind the piston. This releases theresistence of the working fluid, allowing the knocker and anvil to comeinto jarring contact.

The invention will now be described in greater detail with reference tothe drawings wherein:

FIG. 1 illustrates a vertical section of the rotary jar of thisinvention, showing the internal structure.

FIG. 2 is an enlargement of a portion ofFIG. l and illustrates therecess and sleeve combination in the rotary jar of this invention.

The lower portion of integral head and main mandrel 14 has an outsidediameter less than that of box connection 13. This portion is providedwith a plurality of longitudinally directed splines 21, spaced aroundthe circumference, the use of which will be discussed later. The lowestend of the main mandrel 14 is provided with an external thread forreception of knocker 22. The knocker will be described in detail lateras well; it is sufficient to say at this point that it provides themeans for connecting main mandrel 14 to the upper piston mandrel 15which, in turn, is threadedly connected to lower 4 piston mandrel 16.

FIG. 3 is an enlargement of another portion of FIG. 1

and illustrates the valve combination of the invention.

The rotary jar of this invention is shown in cross-section in FIG. 1.Reference numeral 10 designates the rotary jar which, in turn, isconstructed from two mutually extensible basic subassemblies, an innermandrel 11 and an outer housing 12. It is the interaction betweenvarious components of these subassemblies which permits the rotary jarto function as intended.

The inner mandrel 11 is assembled from three cylindrical, hollowsections, namely the integral head and main mandrel.l4, the upper pistonmandrel 15 and the lower piston mandrel 16. In a preferred embodiment ofthe invention the integral head and main mandrel 14includes a boxconnection 13. Box connection 13 is provided with an internal threadwhich may be connected to an external thread on the pin end of a drillstring. Thus, when placed in a drill hole, the box connection 13 wouldbe the uppermost component of the rotary jar 10.

The outer housing 12 is also constructed from three sections, namelyspline housing and impact sub 17,

knocker housing 18 and hydraulic cylinder 19. Each of these sections issubstantially annular in cross-section, the inner diameters thereofbeing greater than the outer diameters of the three inner mandrelsections respectively. The three outer housing sections are threadedlyconnected together, the hydraulic cylinder 19 being the lowermostcomponent of the rotary jar 10 when it is in use in a drill hole. Thelowest portion of hydraulic cylinder 19 is provided with an externalthread to which a drilling tool may be attached.

As mentioned previously, the lower portion of main mandrel 14 isprovided with a plurality of longitudinal splines 21 projecting radiallytherefrom towards the outer housing. Spline housing and impact subs .17has an inner diameter which is slightly greater than the outside shaftdiameter of the lower portion of main mandrel 14. The spline housing 17is provided with a plurality of grooves in its inner wall to correspondto thesplines 21. The interaction between the splines 21 and the groovesprevents any torque from being imparted to the internal parts duringoperation of the rotary jar and also helps prevent any binding betweenthe outer housing and the main mandrel during mutual extension orcontraction.

The length of the spline housing and impact sub 17 is less than that'ofthe lower portion of the main mandrel 14. Thus, longitudinal movement ofthe spline housing and impact sub 17 is permitted between the lowersurface of the box connection 13 and the upper surface of knocker 22. Itis the jar-ring contact between the bottom surface of impact sub 17,which shall henceforth be known as the anvil, and the top surface ofknocker 22 which is the desired effect during operation of the rotaryjar of the invention.

The knocker itself, as mentioned above is threadedly.

connected to the main mandrel 14. It is shaped as an annular collar withan outside diameter essentially the same as the surface diameter of theanvil. In addition to the internal-thread for connection to the mainmandrel, a second internal thread is provided for connection to acorresponding external thread on the upper piston mandrel 15. Since boththe anvil and the knocker are subject to high impact loading, it ispreferable to use hardened steel for their construction.

Knocker housing 18 provides an inner chamber of a diameter slightlygreater than the outside diameter of knocker 22, the relative movementof knocker 22 with respect to housing 18 being confined withinthischamber. Housing 18 has a portion below the knocker which extendsradially inwardly into close proximity with the upper piston mandrel 15.Annular upper packing gland 23 is located in an annular recess in thisportion, the gland providing a fluid-tight seal between the upper pistonmandrel and the housing 18. The gland is held in place by upper glandnut 25 which is threadedly engaged with the inwardly extending portionof housing 18.

Connected to knocker housing 18 by cooperating external and internalthreads is annular hydraulic cylinder housing 19, defining an annularworking chamber 37 between its inner surface and the upper and lowerpiston mandrels 15 and 16. The lower end of the housing 19 is providedwith a radially inwardly extending portion incorporating lower packinggland 24 and lower gland nut 26 in a manner similar to that alreadydescribed .for housing 18. The location of the lower packing gland 24 issuch that even during full relative extension of inner mandrel 11 andouter housing 12, the gland 24 will provide sealing contact with lowerpiston mandrel 16. The longitudinal limits of the working chamber 37 aretherefore the upper and lower packing'glands 23 and 24.

Piston and valve means are attached to the uppe piston mandrel 15 andare located within the working chamber 37. Annular piston 27 is slidablyreceived on mandrel 15 and its outer diameter is sufficiently less thanthe inside diameter of cylinder housing 19 to permit fluid to passbetween the outer and inner wall surfaces respectively. The innerdiameter of piston 27 is substantially greater than the outside diameterof piston mandrel 15 so as to permit the passage of fluid therebetweenas well. Piston 27 is slidable longitudinally along mandrel 15 betweenupper and lower limits provided respectively by a ring 28 which extendsradially outwards from mandrel 15 into working chamber 37, and anannular piston seat 29 which is threadedly attached to mandrel l5andwhich is slightly less in outer diameter than the piston 27 itself.When the outer housing 12 and the inner mandrel 11 are in a fullycontracted or a fully extended relation, the piston and valve means willbe adjacent the lower and upper packing glands 24 and 23 respectively.

The valve means are generally designated by reference numeral 30.Annular seal 31, in the form of a cup, is located between the uppersurface of piston 27 and the lower surface of ring 28. As with piston27, the.

inner diameter of seal or cup 31 is substantially greater than the outerdiameter of piston mandrel 15, but less than the outer diameter of ring28. The outer diameter of cup 31 is actually slightly greater than theinner diameter of cylinder housing 18 so that the cup which isconstructed from a suitably resilient material exerts an outward forceonto the inner surface of cylinder housing 18. Since the frictionbetween the surfaces in contact must .be kept at a minimum, a materialsuch as is sold under the trademark Teflon (R) is recommended for cup31.

A single, longitudinal, small-diameter bore 32 is provided in cup 31 topermit quantities of a working fluid to pass therethrough during mutualextension of mandrel l1 and housing 12. The bore 32 leads to counterbore33 in piston 27, the bores 32 and 33 being on the same centerline.Counterbore 33 is of a larger diameter than bore 32 and extends onlypart way through piston 27. The counterbore may receive valve cartridge34 which is the main factor in restricting the flow of fluid throughvalve means 30. The valve cartridge is a porous material and ispreferably temperature variable so that a high temperature, which wouldreduce the viscosity of a fluid, would expand the cartridge to therebyreduce the porosity and restrict fluid flow. Materials such as porousbrass or bronze are recommended for the valve cartridge 34. Bores 35 and36 are provided in piston 27 and piston seat 29 respectively to takefluid from the valve cartridge 34 to below valve seat 29 (i.e. below cup31). These bores are preferably of the same diameter as, and axiallyaligned with, bore 32.

An annular recess 39 is provided in the inner wall of cylinder housing19. Within the recess is located annular sleeve 40, the inner diameterof which is substantially equal to the inner diameter of housing 19. Thesleeve 40 is smaller than the recess 39 so that fluid may surround thesleeve. When in its rest position, the sleeve 40 is positively forcedlongitudinally against its seat in recess 39 by wave spring 41 which islocated in an annular groove provided in thebottom surface of knockerhousing 18.

Lastly, the working chamber 37 is filled with working fluid 38 whenhousing 12 and mandrel 11 are in their mutually contracted condition. Itis desirable to use a fluid which exhibits small changes in viscosityover a large temperature range. A fluid such as is sold under thetrademark Silicone 200 would be very suitable for this application. Thefluid is introduced into the working chamber 37 through a filling hole,not shown, in cylinder housing 19.

The use and operation of the rotary jar of the invention will now bedescribed in considerable detail. A tool is attached to the lower end ofcylinder housing 19 via threads 20 and the box connection 13 is attachedto a drill string. The working fluid 38 is introduced into workingchamber 37 with the rotary jar in its fully contracted condition. Thetool, rotary jar and drill string are introduced into the drill hole andoperations continue normally. If the tool becomes tightly wedged in thehole, a jarring action may be applied through the rotary jar to attemptto dislodge the tool. This action will now be described.

A vertical strain is applied to inner mandrel 11 through the drillstring. This causes cup 31 and piston 27 to rest solidly on piston seat29, and puts working fluid 38 into compression. Since the only way torelieve the internal pressure in the working fluid is through valve 30,a small portion of fluid will pass through bore 32, porous cartridge 34and bores 35 and 36 into that portion of working chamber 37 which isbetween piston seat 29 and lower packing gland 24. At an extremely slowspeed, the piston 27 valve means 30 will rise, relatively, in workingchamber 37. When cup 31 comes adjacent release sleeve 40 the combinationof wall friction therebetween and fluid pressure behind and aroundrelease sleeve 40 causes the sleeve to move in the same direction as thepiston 27. The working fluid 38 still remaining in compression inchamber 37 will be dumped around the sleeve and behind the cup 31,thereby drastically reducing the resistance of fluid 38 and permittingthe upwards strain to bring knocker 22 into a jarring impact with anvil17. The jarring effect is transmitted through outer housing 12 to thetool which might then be dislodged from its trapped position.

In order to reset the rotary jar of this invention so that it may beused again, it is only necessary to allow the weight of the drill stringabove to be set down on the jar. When this occurs, the piston 27 islifted off valve seat 29 by the fluid 38 captured below it. Thismovement of piston 27, and a corresponding movement of cup 31, opens theseal which was in operation during mutual extension and which forced theworking fluid through porous cartridge 34. Fluid may now travel,rapidly, between the piston seat 29 and piston 27, between piston 27 andpiston mandrel and between cup 31 and piston mandrel 15 into the portionof working chamber 37 located above cup 31. It is, of course, necessaryto provide longitudinal grooves or holes in ring 28 to permit passage offluid, since the cup 31 will be in sealing contact with the lowersurface of ring 28 during mutual contraction of the mandrel 11 andhousing 12. Once the mutual contraction is fully complete, the rotaryjar is ready to deliver another blow when required.

It is readily apparent that the valve means 30 of the rotary jar of thisinvention contains no moving parts. Thus, the probability of failure dueto wear is considerably reduced over jars found in the prior art. Theonly moving parts to be found in the rotary jar of this invention are incontact with seals or packing glands and consequently the probability offailure of these parts is also very small.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A rotary jar for an oil well tool which comprises a tubular housinghaving one end attachable to a well tool, a mandrel extending into saidhousing and having an end portion externally of said housing attachableto a drill string, said mandrel having a splined connection with saidhousing permitting non-rotative reciprocating movement of said mandrelrelative to said housing, said housing having an internal annularshoulder constituting an anvil, said mandrel having an annular shoulderconfronting said internal annular shoulder and constituting a knocker,means forming a substantially confined annular chamber between saidmandrel and housing for reception of a working fluid, a piston in saidchamber slidingly mounted on said mandrel, said mandrel having stopmeans limiting sliding movement of said piston on said .mandrel andoperable to apply reciprocating movement tosaid piston with saidmandrel, said piston having a restricted fluid passage ex tendingtherethrough, control valve means in said passage and sleeve means insaid housing and engagable by said piston to provide a fluid passagearound said piston.

2. A rotary jar according to claim 1 wherein said control valve is aporous metallic cartridge.

3. A rotary jar according to claim 1 wherein said piston includes anannular ring slidably mounted on said mandrel and within said chamber,and wherein said stop means includes an annular rim on said mandrellocated between said ring and said sealing means adjacent said knockerand an annular piston seat on said mandrel and within said chamber.

4. A rotary jar according to claim 3 wherein said control valve meansincludes an annular resilient piston cup within said chamber, having aninner diameter greater than the outside diameter of said mandrel butless than that of said rim and located between said piston and said rim,a small diameter bore through said cup in a direction longitudinal ofsaid mandrel and between said mandrel and housing, a counterbore in saidpiston and having a diameter greater than the diameter of said bore toreceive said porous cartridge, a second small diameter bore in saidpiston axially aligned with said bore and communicating said counterbore with said chamber, and a third small diameter bore through saidpiston seat and axially aligned with said second bore.

5. A rotary jar according to claim 1 wherein said knocker is a collarextending radially outwards from said mandrel into proximity with saidhousing and said anvil is a collar extending radially inwards from saidhousing into proximity with said mandrel.

6. A rotary jar according to claim 4 wherein said splined connectioncomprises radially extending longitudinal splines on said mandrel andextending from said knocker away from said chamber, and longitudinalgrooves in said collar for cooperation with said splines to preventturning of said housing relative to said mandrel.

7. A rotary jar according to claim 5 wherein said cartridge is porousbrass or bronze.

8. A rotary jar for an oil well tool including an inner mandrel adaptedfor attachment to a drill string, an outer housing mutually extensiblewith said mandrel and adapted for attachment to a well tool, splinemeans between said mandrel and housing permitting non-rotative mutualextension of said mandrel and housing, annular knocker means on saidmandrel, annular anvil means in said housing for coaction with saidknocker, annular seal means in said housing, said seals being in sealingcontact with said mandrel, being spaced apart longitudinally in saidhousing in one direction from said knocker and anvil, and defining achamber therebetween in an annular cavity between said mandrel andhousing, said chamber adapted to receive a working fluid which exhibitsonly small viscosity changes with large temperature changes, pistonmeans .slidable on said mandrel and located in said chamber,

of said mandrel and housing and means forming a by-.

pass to said porous cartridge adapted to permit large quantities of aworking fluid to pass therethrough during mutual contraction of saidmandrel and housing,

and means forming a recess in said housing within said chamber adjacentthe seal nearest said knocker and anvil for receiving annular sleevemeans such that when said valve combination and piston are movedadjacent said sleeve during mutual extension of said mandrel andhousing, the sleeve will move with said valve combination and piston topermit rapid flow of a working fluid around said valve combination andpiston effectively bypassing said porous cartridge to permit saidknocker and anvil to come into jarring contact.

9. A rotary jar according to claim 3 wherein said sealing means arecontained in radially inwardly extending portions of said housing ateach end of the chamber so defined and are comprised of packing sleeveis biased away from the sealing means adjacent said knocker by resilientspring means and wherein said recess is sufficiently larger than saidsleeve to permit fluid to surround said sleeve.

1. A rotary jar for an oil well tool which comprises a tubular housinghaving one end attachable to a well tool, a mandrel extending into saidhousing and having an end portion externally of said housing attachableto a drill string, said mandrel having a splined connection with saidhousing permitting non-rotative reciprocating movement of said mandrelrelative to said housing, said housing having an internal annularshoulder constituting an anvil, said mandrel having an annular shoulderconfronting said internal annular shoulder and constituting a knocker,means forming a substantially confined annular chamber between saidmandrel and housing for reception of a working fluid, a piston in saidchamber slidingly mounted on said mandrel, said mandrel having stopmeans limiting sliding movement of said piston on said mandrel andoperable to apply reciprocating movement to said piston with saidmandrel, said piston having a restricted fluid passage extendingtherethrough, control valve means in said passage and sleeve means insaid housing and engagable by said piston to provide a fluid passagearound said piston.
 1. A rotary jar for an oil well tool which comprisesa tubular housing having one end attachable to a well tool, a mandrelextending into said housing and having an end portion externally of saidhousing attachable to a drill string, said mandrel having a splinedconnection with said housing permitting non-rotative reciprocatingmovement of said mandrel relative to said housing, said housing havingan internal annular shoulder constituting an anvil, said mandrel havingan annular shoulder confronting said internal annular shoulder andconstituting a knocker, means forming a substantially confined annularchamber between said mandrel and housing for reception of a workingfluid, a piston in said chamber slidingly mounted on said mandrel, saidmandrel having stop means limiting sliding movement of said piston onsaid mandrel and operable to apply reciprocating movement to said pistonwith said mandrel, said piston having a restricted fluid passageextending therethrough, control valve means in said passage and sleevemeans in said housing and engagable by said piston to provide a fluidpassage around said piston.
 2. A rotary jar according to claim 1 whereinsaid control valve is a porous metallic cartridge.
 3. A rotary jaraccording to claim 1 wherein said piston includes an annular ringslidably mounted on said mandrel and within said chamber, and whereinsaid stop means includes an annular rim on said mandrel located betweensaid ring and said sealing means adjacent said knocker and an annularpiston seat on said mandrel and within said chamber.
 4. A rotary jaraccording to claim 3 wherein said control valve means includes anannular resilient piston cup within said chamber, having an innerdiameter greater than the outside diameter of said mandrel but less thanthat of said rim and located between said piston and said rim, a smalldiameter bore through said cup in a direction longitudinal of saidmandrel and between said mandrel and housing, a counterbore in saidpiston and having a diameter greater than the diameter of said bore toreceive said porous cartridge, a second small diameter bore in saidpiston axially aligned with said bore and communicating said counterbore with said chamber, and a third small diameter bore through saidpiston seat and axially aligned with said second bore.
 5. A rotary jaraccording to claim 1 wherein said knocker is a collar extending radiallyoutwards from said mandrel into proximity with said housing and saidanvil is a collar extending radially inwards from said housing intoproximity with said mandrel.
 6. A rotary jar according to claim 4wherein said splined connection comprises radially extendinglongitudinal splines on said mandrel and extending from said knockeraway from said chamber, and longitudinal grooves in said collar forcooperation with said splines to prevent turning of said housingrelative to said mandrel.
 7. A rotary jar according to claim 5 whereinsaid cartridge is porous brass or bronze.
 8. A rotary jar for an oilwell tool including an inner mandrel adapted for attachment to a drillstring, an outer housing mutually extensible with said mandrel andadapted for attachment to a well tool, spline means between said mandreland housing permitting non-rotative mutual extension of said mandrel andhousing, annular knocker means on said mandrel, annular anvil means insaid housing for coaction with said knocker, annular seal means in saidhousing, said seals being in sealing contact with said mandrel, beingspaced apart longitudinally in said housing in one direction from saidknocker and anvil, and defining a chamber therebetween in an annularcavity between said mandrel and housing, said chamber adapted to receivea working fluid which exhibits only small viscosity changes with largetemperature changes, piston means slidable on said mandrel and locatedin said chamber, means forming a valve combination within said chamberwhereby said valve combination includes a porous cartridge adapted topermit minute quantities of a working fluid therethrough during mutualextension of said mandrel and housing and means forming a by-pass tosaid porous cartridge adapted to permit large quantities of a workingfluid to pass therethrough during mutual contraction of said mandrel andhousing, and means forming a recess in said housing within said chamberadjacent the seal nearest said knocker and anvil for receiving annularsleeve means such that when said valve combination and piston are movedadjacent said sleeve during mutual extension of said mandrel andhousing, the sleeve will move with said valve combination and piston topermit rapid flow of a working fluid around said valve combination andpiston effectively bypassing said porous cartridge to permit saidknocker and anvil to come into jarring contact.
 9. A rotary jaraccording to claim 3 wherein said sealing means are contained inradially inwardly extending portions of said housing at each end of thechamber so defined and are comprised of packing glands held in place bygland nuts, each gland nut being annular in shape and having an externalthread for coaction with an internal thread in said housing adjacentsaid packing gland.